What is the game Kingdom Hearts about

Long story, but I'll make it short. It's about a boy called Sora, he has 2 bestfriends, Kairi & Rikku. One stormy night, a huge black thing appears along with little sidekicks called 'Heartless'. Rikku got sucked in by the darkness first and Sora find a mysterious door, it starts opening, a few seconds later, he ended up in a town with a forgotten name, he tries finding his friends, so he sets off with an adventure with 2 friends, Goofy and Donald to find Sora's missing friends. Then KH2 Appears. Some sentences might not make sense. Lol.